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Preeclampsia is a pregnancy induced hypertension that can be associated with proteinuria (an excess of serum proteins in the urine) and edema. Preeclampsia typically occurs in 5-10% of pregnancies, and is characterized by symptoms such as swelling, sudden weight gain, headaches and changes in vision. Preeclampsia can progress to eclampsia, with cerebral symptoms leading to convulsions. The condition is associated with systemic vasospasm wherein arteries throughout the body narrow. This can lead to multi-organ system dysfunction wherein many organs of the body, including the kidneys, brain, eyes, liver, etc., are unable to function normally because of altered blood flow and increased blood pressure. Currently the only effective treatment is delivery of the fetus and placenta. Typically, preeclampsia occurs after 20 weeks gestation (in the late 2nd or 3rd trimester), though it can occur earlier.
While the cause of preeclampsia is still being debated, inadequate blood supply to the placenta, abnormalities in the immune system and maternal endothelial cell dysfunction are suspected to be involved. A theorized cause of preeclampsia is compression of the left renal vein due to increased abdominal pressures caused by the growing uterus and abdomen during pregnancy. Abdominal organs can shift due to the growing uterus and can pin the left renal vein, which passes between the vertebra and the aorta, against the rigid aorta causing the blood pressure within the left renal vein to increase substantially. The increase in blood pressure within the left renal vein activates a biological system in the kidney which in effect causes increased system blood pressure, or hypertension. Other circumstances can also trigger the hypertension symptoms, for example, obesity can cause external forces to be exerted on the left renal vein against the aorta, leading to a higher than normal renal vein pressure resulting in hypertension and preeclampsia symptoms.